The present invention relates to delay line assemblies and in particular to an improved method and construction for forming such assemblies on a flexible substrate which accommodates a fan folded packaging arrangement.
Transmission line assemblies having predetermined, equally distributed signal delay characteristics have heretofore typically been constructed on rigid substrate materials using a variety of processing techniques. The time delay characteristic of any such device being principally determined by the physical length of the transmission line. Other device characteristics of concern are the numbers and relative positioning of adjacent ground planes and the type and thickness of associated dielectric insulators separating the transmission line and ground layers, which affect the distributed inductance and capacitance.
Where too such devices are incorporated in high frequency applications, a ceramic supporting substrate material such as aluminum oxide is typically preferred. A problem attendant with the use of such substrates however is that of physical size limitations of the material for a given thickness substrate which economically limits the device size, unless multi-layering techniques are employed. Also, as additional layers are added, fabrication costs rise and yields decrease. Preferably, therefore, a maximum yield is achieved which a two dimensional assembly, but which again is limited by the physical characteristics of the substrate material.
Various rigid substrate delay line devices of which Applicant is aware can be seen in U.S. Pat. Nos. 4,641,114; 4,641,113; 3,257,629 and 2,832,935. Applicant's pending U.S. application Ser. No. 180,353 entitled Thin Film Delay Lines discloses another device which uses a rigid substrate.
As a solution to the foregoing problems, Applicant has developed a method and apparatus wherein two-dimensional processing techniques may be employed to produce a modularly organized, flexible or non-rigid assembly. Such an assembly further facilitates device construction by way of enabling fan-folding relative to multiple sections of transmission line which can further be cut to a desired length.